Ischaemic stroke and TIA risk in COVID-19 patients lower than previously believed, study finds

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Saate Shakil

The elevated risk of ischaemic stroke and transient ischaemic attack TIA in hospitalised COVID-19 patients may be lower than previously reported—although it is still higher than the risks associated with influenza and other infections, a late-breaking presentation at the International Stroke Conference (ISC) 2021 (17–19 March, virtual) reports.

Saate Shakil—lead author of the study and a fellow in the Division of Cardiology at the University of Washington’s School of Medicine (Seattle, USA)—stated that, across a sample of 21,073 hospitalised COVID-19 patients, the risk of death was also more than twice as high in those who experienced ischaemic stroke or TIA compared to those who did not.    

According to Shakil, the potential for increased ischaemic stroke risk in COVID-19 patients was first noted in spring 2020, as the pandemic began to affect the USA more severely—with multiple studies published last year finding the occurrence of ischaemic strokes to be between 0.9% and 2.8%, compared to about 0.2% in influenza patients. A further American multicentre study published in early 2021 found an ischaemic stroke incidence of 1.3% among 8,163 COVID-19 patients.   

Shakil and her co-authors used the American Heart Association (AHA) COVID-19 registry to further this existing research, and identified a subset of 21,073 patients hospitalised with an active COVID-19 infection, across 160 US hospitals, between March and November 2020, giving them a sample size that was “much larger” than any of those used in previous studies of ischaemic stroke risk among COVID-19 patients.  

The study found that, in this cohort, there was a total number of 289 strokes, representing 1.4% of the sampled patients. Of these 289 strokes, 152 (52.6%) were ischaemic strokes, and eight (2.8%) were TIAs—resulting in a total of 160 ischaemic cerebrovascular events.   

The researchers therefore calculated an overall ischaemic stroke or TIA incidence of about 0.75% within their sample of 21,073 hospitalised COVID-19 patients. As Shakil said, while this percentage is lower than the 0.92.8% range previously suggested by other, smaller-scale investigations, it is higher than the 0.2% incidence of ischaemic stroke among influenza patients.   

In addition, the study found that several comorbidities—including hypertension, cerebrovascular disease, coronary artery disease (CAD), diabetes and atrial fibrillation—had a “significantly higher prevalence” among COVID-19 patients who experienced an ischaemic stroke or TIA, compared to patients who did not.  

According to Shakil, there was also a higher prevalence of critical illness features and poor in-hospital outcomes among those COVID-19 patients who did experience an ischaemic stroke or TIA, as they had to stay in hospital for roughly twice as long, on average.  

Hospitalised COVID-19 patients who experienced an ischaemic cerebrovascular event were found to have more than double the percentage of in-hospital mortality rates compared to those who did not, while increased rates of intensive care unit (ICU) admission, mechanical ventilation and renal replacement therapy were also observed within the sample.   

Shakil also stated that, alongside its goal of assessing the prevalence of ischaemic stroke among people hospitalised with COVID-19, the study initially intended to find out if there were any racial disparities within this group of patients.  

It found that disparities based on race and ethnicity did exist to some extent, as non-Hispanic Black patients accounted for 31% of all ischaemic stroke patients in the sample—compared to their overall representation in the AHA registry, which was 27%—while this trend was reversed among Hispanic patients, as the percentage of ischaemic stroke patients in this group was far lower than the overall percentage of Hispanic COVID-19 patients in the registry.   

The researchers also found that ischaemic stroke risk in the sample was highest among non-Hispanic black patients, with an above-average incidence of 0.91%, followed by non-Hispanic white patients and Hispanic patients, who had ischaemic stroke incidences of 0.75% and 0.52%, respectively. This was in spite of non-Hispanic white patients being, on average, the oldest racial or ethnic group in the sample, with a mean age of 67.7 years, compared to mean ages of 63.5 years and 63.1 years, respectively, in the Hispanic and non-Hispanic Black patient groups.   

The study concluded that hospitalised COVID-19 patients who experienced an ischaemic stroke or TIA were more likely to be older, male, and with a higher prevalence of comorbidities like atrial fibrillation, diabetes and hypertension than those without stroke or TIA.  

Regarding future research directions, Shakil stated that there is a need to evaluate the temporal and geographical changes in ischaemic stroke and TIA risk among COVID-19 patients—and an adjusted analysis of the study’s outcomes by race, comorbidities and illness severity, and an assessment of the longer-term impact of COVID-19 on cardiovascular and stroke risks, should also be conducted.  


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